alienfx: also build on i686

pkgs/os-specific/linux/alienfx/default.nix

···
     description = "Controls AlienFX lighting";
     homepage = "https://github.com/tibz/alienfx";
     maintainers = [stdenv.lib.maintainers.tomberek];
-    # Has only been tested on M11x
-    platforms = [ "x86_64-linux" ];
+    platforms = stdenv.lib.platforms.linux;
   };
 }